Right, I've had a look at the sensor - basically it seems as though the sensor is quite far away from the hose - I can rotate the metal bit (and sensor) inside the hose, but the sensor is tight on the metal bit....
Make sense?
The metal insert in the tube means that the sensor is about 1/2 inch away from the hose - the metal bit sticks out of the hose...
I've had a grab of hoses but all look ok....